IC package hold-down fixture

Abstract

The present invention involves a hold-down fixture which is usable in connection with bonding an integrated circuit package to a printed circuit board in a surface mount environment. The purpose of the fixture is to hold each of the leads of the package in intimate contact with corresponding contact pads on the printed circuit board during the bonding process. The fixture includes a base with two bars for each group of leads extending from the perimeter of the housing of the package. Together the bars compressively force the entire foot of each lead to set flatly against its pad. The bars are spaced such that an aperture, which is defined by an opening through the base and positioned between the bars, can admit a bonding means, such as a laser beam, to reflow a solder composition at the lead/pad junction. Accordingly, with the leads compressed against the pads by the bars of the fixture, and with the reflow of the solder composition by means of the laser, a good bond between each lead and pad will be formed.

What is claimed is: 
     
       1. An apparatus for holding a first electrically conductive element in contact with a second electrically conductive element while said first and second elements are being bonded, said apparatus comprising: a base means having an aperture therethrough;   a first hold-down means, said first hold-down means adjoining said base means and being made of a compliant material such that it is capable of elastically deforming with said first hold-down means in compressive force contact with a first portion of said first, conductive element; and   a second hold-down means, said second hold-down means adjoining said base means and being spaced in relation to said first hold-down means such that said aperture is positioned between said first and second hold-down means, said second hold-down means being positioned on said base such that with said first hold-down means in compressive force contact with said first portion of said first conductive element, said second hold-down means compressively engages a second portion of said first conductive element, said compressive force of said first and second hold-down members thereby holding said first and second conductive elements in intimate contact for bonding.   
     
     
       2. An apparatus as in claim 1, wherein said aperture is positioned such that with said first and second conductive elements held in intimate contact, said aperture exposes a portion of said first conductive element which is in contact with said second conductive element. 
     
     
       3. An apparatus as in claim 1, wherein said first and second hold-down means are comprised of a first and second bar, respectively. 
     
     
       4. An apparatus as in claim 3, wherein said first bar is comprised of an elastomeric material having a durometer between 30-70 on the Shore A scale. 
     
     
       5. An apparatus as in claim 1, further comprising an adjustment means for adjusting the relative height between said first and second bars, said adjustment means adjoining said base means. 
     
     
       6. An apparatus for holding a lead of an integrated circuit package in intimate contact with a corresponding contact pad while said lead and pad are being bonded by a bonding means to said pad, said apparatus comprising: a base means having an aperture therethrough;   a first hold-down means, said first hold-down means adjoining said base means and being made of a compliant material such that it is capable of elastically deforming with said first hold-down means in compressive force contact with a first portion of said lead; and   a second hold-down means, said second hold-down means adjoining said base means and being spaced in relation to said first hold-down means such that said aperture is positioned between said first and second hold-down means, said second hold-down means being positioned on said base such that with said first hold-down means in compressive force contact with said first portion of said lead, said second hold-down means compressively engages a second portion of said lead, said compressive force of said first and second hold-down members thereby holding said lead and pad in intimate contact for bonding.   
     
     
       7. An apparatus as in claim 6, wherein said aperture is positioned such that with said lead and pad held in intimate contact, said aperture exposes a portion of said lead which is in contact with said pad. 
     
     
       8. An apparatus as in claim 6, wherein said first and second hold-down means are comprised of a first and second bar, respectively. 
     
     
       9. An apparatus as in claim 8, wherein said first bar is comprised of an elastomeric material having a durometer between 30-70 on the Shore A scale. 
     
     
       10. An apparatus as in claim 6, further comprising an adjustment means for adjusting the relative height between said first and second bars, said adjustment means adjoining said base means. 
     
     
       11. An apparatus for holding a plurality of leads of an integrated circuit package in intimate contact with a plurality of corresponding contact pads while said leads and pads are being bonded by a bonding means, said leads each having a first and second bent portion, said first and second bent portions being generally parallel to one another such that said first and second bent portions are separated by a given distance "h", said apparatus comprising: a base means having an aperture therethrough;   a first hold-down means, said first hold-down means adjoining said base means and being made of a compliant material such that it is capable of elastically deforming with said first hold-down means in compressive force contact with said first bent portions of said leads; and   a second hold-down means, said second hold-down means adjoining said base means and being spaced in relation to said first hold-down means such that said aperture is positioned between said first and second hold-down means, said second hold-down means being positioned on said base such that with said first hold-down means in compressive force contact with said first bent portions of said leads, said second hold-down means compressively engages said second bent portions of said leads, said compressive force of said first and second hold-down members thereby holding corresponding leads and pads in intimate contact for bonding.   
     
     
       12. An apparatus as in claim 11, wherein said aperture is positioned such that with said leads and pads held in intimate contact, said aperture exposes a portion of each of said leads which is in contact with each of said corresponding pads. 
     
     
       13. An apparatus as in claim 12, wherein said first and second hold-down means each has a respective contact surface, and said contact surface of said first hold-down means has a height difference relative to said contact surface of said second hold-down means equal to "h". 
     
     
       14. An apparatus as in claim 11, wherein said first and second hold-down means are comprised of a first and second bar, respectively. 
     
     
       15. An apparatus as in claim 14, wherein said first bar is comprised of an elastomeric material having a durometer between 30-70 on the Shore A scale. 
     
     
       16. An apparatus as in claim 11, further comprising an adjustment means for adjusting the relative height between said first and second bars, said adjustment means adjoining said base means. 
     
     
       17. An apparatus as in claim 16, wherein said adjustment means comprises a shim. 
     
     
       18. An apparatus as in claim 11, wherein said bonding is accomplished by means of a laser, and said first hold-down means comprises a material which is coupled with the characteristics of said laser such that said laser does not damage said first hold-down means in operation. 
     
     
       19. A method for bonding a first electrically conductive element to a second electrically conductive element, said method comprising the steps of: aligning said first conductive element with said second conductive element;   compressively forcing a first portion of said first conductive element into contact with said second conductive element, by means of a first hold-down means having the ability to elastically deform under said compressive force;   compressively forcing a second portion of said first conductive element in the direction of said second conductive element by means of a second hold-down means, said compressive force of said first and second hold-down members holding said first conductive element in intimate contact with said second conductive element; and   heating said first and second conductive elements with a bonding means.   
     
     
       20. A method for bonding each of a plurality of leads on an integrated circuit package to a plurality of contact pads, such that each lead corresponds to one pad, said leads each having a first and second bent portion, said first and second bent portions being generally parallel to one another, said method comprising the steps of: aligning said first bent portion of each of said leads with its corresponding pad;   compressively forcing said first bent portion of each of said leads into contact with its corresponding pad, by means of a first hold-down means having the ability to elastically deform under said compressive force;   compressively forcing said second bent portion of each of said leads in the direction of its corresponding pad by means of a second hold-down means, said compressive force of said first and second hold-down means holding said first bent portion of each of said leads in contact with its corresponding pad; and   heating said lead/pad combinations through a bonding means.   
     
     
       21. The method as in claim 20, wherein said bonding means is a laser beam, and said beam is directed to said lead/pad combinations by passing said beam between said first and second hold-down means. 
     
     
       22. The method as in claim 21, wherein said first hold-down means comprises a material which is coupled with the characteristics of said laser such that said laser does not damage said first hold-down means in operation.